The plasma mass of apolipoproteins A-I and apolipoproteins A-II was examined in 14 normal individuals selected at random following 10 days of stabilization on a metabolic diet. ApoA-II had become stable in more than 80 percent of the subjects while A-I was stable in 60 percent. Using statistical models fasting and non-fasting determinations of apoA-II were found to be equal while a parallel examination of apoA-I mass found the non-fasting values to be elevated by one-half standard deviation. Triglyceride kinetics were studied in hyperlipidemic subjects utilizing radiolabeled glycerol before and following therapy with nicotinic acid. Analysis using a compartmental model revealed that nicotinic acid decreases the residence time of VLDL-triglyceride without a significant change in the absolute synthesis rate. Changes in triglyceride kinetics following drug treatment resulted in secretion of more VLDL or an unchanged number of VLDL containing more triglyceride but usually not both. Triglyceride kinetics examined in Pima Indians using a compartmental model were found to correlate with post-prandial plasma free fatty acid levels; synthesis rate r equals .76 p less than .005 a strict precursor product relationship between VLDL and LDL did not exist.